1. Field of Invention
The present invention relates to medical devices. More particularly, the invention relates to occluding devices and methods of occluding fluid flow through a body vessel.
2. Background of the Invention
Pushable fibered coils have been used as a primary occluding device for treatment of various arteriovenous malformations (AVM) and varicoceles, as well as for many other arteriovenous abnormalities in the body. Occluding devices are also used to repair abnormal shunts between arteries and veins, prevent or reduce blood flow to tumors, stop hemorrhaging as a result of trauma, and stabilize aneurysms to prevent rupture. Pushable fibered coils may be configured in a variety of sizes with varying diameters and may be made of several different materials including stainless steel and platinum.
Although current pushable fibered coils are adequate, such coils may be improved for more effective occlusion of fluid flow through a lumen of a body vessel. Many medical procedures for occluding blood flow through an artery or vein require a number of coils, since a single coil or two may not be sufficient to effectively occlude blood flow through a lumen of an artery or vein. In many current procedures, many coils may be packed within each other to produce effective cross sectional occlusion of fluid flow through a body vessel. In some instances, these procedures may involve an undesirable amount of additional time and costs.
Many pushable fibered coils are designed with high tension or stiffness, e.g., between about 60 to 100 weight grams, to wedge or attach strands of fiber to the coils. Upon deployment in a body vessel for occlusion, such coils tend to reform or recanalize back to its helical shape because of the high tension. The helical shape of the coils creates an undesirable opening through which fluid may flow, thereby requiring additional coils to be deployed in the body vessel.
For example, prior art FIGS. 1a-1d depict typical prior art coils. FIG. 1a shows a prior art coil 702 deployed in a body vessel 704 for treatment of various AVM and varicoceles and other arteriovenous abnormalities. Prior art coil 702 has a relatively high initial tension, e.g. greater than 60 weight grams, which contributes to reformation of the coil 702 back to its helical shape in the vessel 704. As depicted in FIG. 1b, the strands 706 of fiber attached to the coil 702 are concentrated around the periphery of the vessel 704. Rather than occlusion, the vessel 704 only experiences a reduced lumen through which blood may still flow, requiring further embolotherapy. As a result, more occluding devices are added until the lumen is filled or occluded.
Prior art FIG. 1c is a pulmonary angiogram 710 in the arterial phase and prior art FIG. 1d is a pulmonary angiogram 720 in the venous phase, each depicting conventional coils 712 and 714 in the pulmonary vasculature 716 after an initial embolotherapy procedure of a pulmonary AVM. Conventional coils 712 and 714 are made of stainless steel and have a relatively high initial tension. As shown, conventional coils 712 and 714 have reformed back and re-opened to their helical shape after the initial procedure, allowing blood flow through the coil in the blood vessel. In this example, further embolotherapy is recommended to occlude the vessel.
Due to the short length of pushable fibered coils, a practitioner may experience difficulty in accurately deploying a coil at a desired location in a body vessel. Pushable fibered coils are short in length, e.g., 2 to 4 centimeters. During deployment, the coil contacts the wall of a body vessel to be occluded. Upon contact with the wall, the coil typically becomes fully deployed from a catheter in the body vessel, thereby preventing the practitioner from adjusting the location of the coil.
Additionally, due to the short length of pushable fibered coils, there is a concern that current coils are difficult to advance through a catheter. A pushable fibered coil has fibers packed along the length of the coil. Due to its short length, the fibers fold or bend over each other when the coil is loaded in a catheter. As a result, the coil has an enlarged diameter to be advanced through the catheter, thereby creating an undesirable resistance to the practitioner.